The present invention relates to the field of battery charging. Specifically, the present invention relates to a method and system for extending battery life by preventing charging when the battery""s temperature is out of an acceptable range.
Two significant problems occur if a battery is charged outside of a suitable temperature range. First, the number charge/discharge cycles the battery is capable of is reduced. For example, charging Lithium polymer batteries below zero or above 40 degrees Celsius reduces lifetime. Batteries other than Lithium polymer are affected by this phenomena as well. Secondly, charging at too high a temperature can damage the battery or even cause the battery to explode. For example, a Lithium polymer battery may explode if charged above 90 degrees Celsius.
A conventional system for monitoring a battery""s temperature is described in U.S. Pat. No. 5,557,188. That patent describes a method of protecting against charging or discharging a battery when the temperature is too high. If a temperature sensor detects that the battery""s temperature is too high, a charging circuit is broken, thus disconnecting the battery from the power supply and the device the battery powers. Unfortunately, the battery may not be used to power an electronic device when the temperature is out of range because the path between the battery and the electronic device is broken when the charging circuit is broken. Additionally, the temperature sensor is disclosed as only monitoring for a temperature which is above a certain range. However, Lithium polymer batteries may have their lifetime""s reduced if charged when the temperature is too low.
With other conventional systems, the charging current supplied to the battery is reduced as the battery""s temperature increases. Unfortunately, these systems are not well-adapted for batteries such as Lithium polymer, which do not need to have the charging current reduced as the battery""s temperature rises. Consequently, the time to charge a Lithium polymer battery may be unnecessarily increased when using such a conventional system.
Some conventional systems display a symbol to indicate that a battery is being charged. However, if the battery is not being charged because the temperature is out of range, these conventional systems do not explain why the battery is not being charged. In some cases, the user of the electronic device could rectify the temperature problem if the user knew what the problem is. However, the problem may not be rectified due to lack of notification.
Therefore, it would be advantageous to provide a method and system for preventing a battery from charging while its temperature is outside of an acceptable range. A further need exists for such a method and system which detects both an upper and a lower temperature bound. A still further need exists for such a method and system which provides a charging current to the battery which is independent of the battery""s temperature over the acceptable temperature range. A still further need exists for such a method and system in which the battery may be used to power, for example, a portable electronic device, even if the temperature is out of range and battery charging is disabled. A still further need exists for such a method and system which displays a message explaining that the battery is not charging because the battery temperature is outside of an acceptable charging range.
The present invention provides a method and system for preventing a battery from charging while its temperature is outside of an acceptable range. Embodiments provide for such a method and system which detects both an upper and a lower temperature bound. Embodiments provide for such a method and system which provides a charging current to the battery which is independent of the battery""s temperature. Embodiments provide for such a method and system in which the battery may be used to power, for example, a portable electronic device, even if the temperature is out of range and battery charging is disabled. Embodiments provide for such a method and system which displays a message explaining that the battery is not charging because the temperature is outside of an acceptable charging range. The present invention provides these advantages and others not specifically mentioned above but described in the sections to follow.
A method and system for controlling battery charging is disclosed. One embodiment provides for a system comprising a battery charging device, a temperature sensor, and a controller. The battery may be a Lithium polymer battery, or the like. The temperature sensor senses the battery temperature and outputs a temperature data signal. The controller inputs the temperature data signal and determines if the battery""s temperature is outside of a range with an upper limit and lower limit. If so, the controller disables the battery charging circuit, wherein the battery is prevented from being charged. In this fashion, the battery""s lifetime (e.g., number of charge/discharge cycles) is extended.
In another embodiment, the system further comprises a display. The controller outputs a signal to the display, directing it to display a message indicating that the battery is not being charged because the temperature is out of a pre-determined range. The message may indicate whether the temperature is too high or too low, in one embodiment.
In yet another embodiment, the battery remains electrically connected to a portable electronic device while the battery charging circuit is disabled from charging. Therefore, the battery may power the portable electronic device while the battery charging circuit is disabled from charging. The portable electronic device may be, for example, a personal digital assistant.
Another embodiment provides for a method of controlling battery charging. The method first monitors the temperature of a battery. Next, the method determines whether the temperature is outside of a range with an upper limit and a lower limit. Then, if the temperature is outside of the range, a battery charging device is disabled. Therefore, the battery is prevented from being charged.